In communication devices, such as Code Division Multiple Access (CDMA) Global System for Mobile communications (GSM) and Wireless Local Area Network (WLAN) communication devices, the ability to detect jammer signals is necessary to improve the performance of the communication device. Communication devices include receiver circuits, which utilize correlation circuits to decipher a desired communication signal from all other received signals. Device performance is degraded when jammer signals are present during the correlation process.
Jammer signals can be introduced by internal or external sources. An internal jammer signal is a jammer signal which is introduced by the receiver. An example is a clock spur generated by a voltage controlled oscillator (VCO) within the receiver.
An external jammer signal is a jammer signal, which is introduced by a source external to the receiver. An example is a signal transmitted by a transmitter in another communication device that generates out-of-band emissions in the receive frequency band of the receiver.
A jammer signal impacts the sensitivity of a receiver in two ways. It can for example de-sense an analog-to-digital converter in the receiver thereby degrading its sensitivity. A jammer signal that appears at odd harmonics of a local oscillator signal in the receiver is down converted into the receive band to degrade signal sensitivity at baseband. Thus, errors may be introduced into the demodulated data packet when jammer signals are not detected by the receiver.
All jammer signals can thus degrade the performance of the receiver within the communication device, and ultimately the device's ability to process signals. Therefore, the ability to detect as many jammer signals as possible, even very low power jammer signals, helps to improve the performance of the receiver within the communication device.
In a typical CDMA device, for example, when a CDMA jammer signal is present, the receiver goes into protected mode where a decision is made by a jammer detector. The jammer detector detects close in jammer signals, such as jammer signals close to the receive (RX) band. A wideband jammer detector is capable of also detecting jammer signals hundreds of MHz away from the RX band. A jammer detector allows the receiver to operate in an un-protected or low power mode when no jammer signal is present and in protected or high power mode in the presence of jammer signals.
There is a need for a wideband jammer detector capable of detecting low power jammer signals over a wide bandwidth while consuming a minimal amount of power.